Metals are indispensable material for human beings. They normally do not exist as simple substances, i.e., zero-valent metals, in nature; most are found, for example, in ores as compounds and mixtures. To obtain metals in simple substance form, ores need to be smelted to extract the metals.
Many methods to extract metals exist, one of which is to reduce ores at an appropriate temperature using a reducing agent. Taking iron extraction as an example, the traditional method includes the blast furnace method. Other commonly used metallurgical methods for iron reduction include, for example, direct reduction and melt reduction. Direct iron reduction falls primarily into two categories: (1) gas-based direct reduction, including, for example, the Midrex shaft kiln method and the HYL reaction tank method; and (2) coal-based direct reduction, including, for example, the Fastmet method using a ring back converter, the CRIMM method using a rotary kiln, the Fastmelt method, and the ITmk3 method. Most of those methods usually require a high concentration of iron, such as over 60% of iron, in the ores. Another coal-based direct reduction method uses tunnel kilns and the reactant materials are in a powder form before entering into the tunnel kiln. Melt reduction methods include, for example the Corex method, the Hismelt method, the Finex Method, and others such as the DIOS, AISI, and CCF methods. Another commonly-used method is the Hoganas method.
These above-mentioned methods, in general, may require high energy consumption, create serious air pollution, or require significant investments for equipment. In addition, these methods may have stringent demand for high-quality feed material, such as requiring high metal-content ores, or requires stringent control during the processing to avoid poor-quality products. Hence, there is still a great need for a new metal reduction process to solve at least one of the problems set forth above.